1. Field of the Invention
The present invention relates to gemstones and, more particularly, to a unique cut for improving the gemstone's light performance including brightness, scintillation and dispersion.
2. Description of the Related Art
The quality of a gemstone such as a diamond is partially dependent upon the cut of the facets which reflect the brilliance, fire, sparkle and luster of a diamond. Facets are the smooth surface areas of a gemstone which have been cut, polished and positioned at different angles (slope and azimuth) which allow light to enter and reflect back from the gemstone. The depth and width and the uniformity of the facets control the brilliance and the durability of a gemstone. The quality of the facets are the major determining factor in enhancing a gemstone's ability to sparkle or reflect light and play a large part in the resulting brilliance of the gemstone. The following general definitions will help with understanding diamond facets.
Brilliance is the amount of sparkle a gemstone gives off through the reflection and refraction of light. Light enters the gemstone through the crown, hits one pavilion side, bounces to the opposite pavilion side and then is reflected back through the crown to the viewer. All facets must support the critical angle in order to achieve this light interaction. Failure to work around the critical angle will cause light entering the crown to exit the stone through the pavilion, instead of through the crown, resulting in a dark and dull stone. Exiting through the pavilion is termed leakage.
Sparkle is a measure of the light reflected out by a gemstone as it is viewed from different angles.
Dispersion, also known as fire, refers to the prism of light refracted from within a cut and polished gemstone and relates to the sparkling colors that are emitted from the stone as it is viewed from different angles. Dispersion is based upon the refractive index, a measure of the degree to which light bends as it passes from air to the stone. Diamonds have one of the highest refractive indexes for natural transparent gemstones. Dispersion is influenced by the facet angles which control the manner in which light enters and exits the gemstone, the number of internal facets in the stone design and the number of times the light rays spread across the facet junctions of the stone. These factors directly affect the fire produced by a finished diamond and thus dispersion is also affected by the manner in which the stone is cut and the angles employed in that cut.
Fluorescence is an inherent property possessed by diamonds resulting in glowing without an appreciable rise of temperature when exposed to ultra-violet rays, cathode rays, etc.
Luster is used to describe the brightness of an object that shines with reflected light rather than producing its own.
Scintillation occurs when light bounces among the facets creating a sparkling display. Good examples of scintillating diamonds are commonly found in round brilliant cuts. They display an eight-pointed star, radiating from the culet when viewed from the table. Optimal scintillation displays a pleasing even pattern of white flashes that results from proper facet symmetry. This is created by light areas turning dark and vice versa, in which dark areas are created by the observer/viewer obscuring light in the angular range from 75 to 90 degrees. The scintillation effect occurs when the diamond moves, the observer/viewer moves or the light source moves causing facets to alternate from illuminated to obscured or light to dark in varied intensities.
Culet is a tiny flat facet that cutters sometimes add to the bottom of a diamonds pavilion to protect the tip of the pavilion from being chipped or damaged.
Cut, including the facet arrangement, is the human contribution to a gemstones beauty and directly affects the qualities of brilliance, scintillation and dispersion. Modern diamond cuts are the result of hundreds of years of study and experimentation on how to best display these unique features of gemstones. From a business standpoint, it is desirable to create new and recognizable cuts for the discerning buyer as a diamond must stand out as a stylish alternative to traditional cuts in order to attract buyers. As a result, several cuts that most effectively optimize brilliance, scintillation and dispersion have become industry standards. Traditional gemstone cuts may be classified into three general categories: the brilliant cut, the step cut, the hybrid or mixed cut.
The brilliant cut is traditionally used to create a round cut stone. It employs triangular facet patterns that radiate from the central table facet towards the girdle edge. The pavilion mains radiate from the cutlet towards the girdle edge. This arrangement produces maximum brilliance, forcing all of the light that enters the crown to be reflected and refracted back through the crown. As such, the brilliant cut maximizes the fire, thereby producing a highly recognizable and marketable stone. Many variations of the brilliant cut exist.
A step cut is a rectangular or square shaped cut. The crown is formed of three concentric rows of trapezoidal facets cut parallel to the girdle and radiating outward from an octagonally shaped table facet having beveled corners. There are two pairs of opposing pavilion sides and four pavilion corners. The pavilion also has three concentric rows or steps between the girdle and the cutlet, each step consisting of eight trapezoidal facets cut parallel to the girdle.
Hybrid or mixed cuts employ a combination of brilliant and step cuts to achieve the classic look of a step cut stone with the brilliance and dispersion closer to that of a brilliant cut stone.
Turning now to a few examples, United States Patent Number (“U.S. Pat. No.”) 7,146,827 to Mardkha is titled Mixed Cut Gemstone. It illustrates a mixed cut gemstone comprising a girdle, a crown above the girdle and a pavilion below the girdle. The crown has a girdle break, a table break and a table. The table break is cut with triangular shaped facets and the girdle break is cut with triangular and quadrilaterally shaped facets. The present invention also describes a pavilion having a width and a length formed by two pairs of opposing pavilion sides and four pavilion corners. The pavilion is composed of four steps including: a first step descending from said girdle to a first step facet junction, a second step descending from said first step facet junction to a second step facet junction, a third step descending from said second step facet junction to a third step facet junction, and a fourth step descending from said third step facet junction to said culet.
U.S. Pat. No. 7,000,607 to Davidi is titled Gemstone and Corresponding Method of Cutting. It shows a gemstone having a crown, a girdle and a pavilion, wherein the girdle is shaped such that, when viewed in plan view, it is primarily bounded by four pairs of parallel straight edges. Three of the four pairs of edges are spaced by roughly equal spacing D.sub.1, while the remaining pair of edges is spaced by a spacing D.sub.2, wherein D.sub.2 is greater than D.sub.1 by between 10% and 40%. Also provided is a method for cutting such a gemstone.
U.S. Pat. No. 6,761,044 to Samuels is titled Gemstone Cut. It illustrates a gemstone cut comprising a crown, a girdle, and a pavilion, wherein the gemstone includes precious gemstones (such as diamonds) and semi-precious gemstones. The crown includes an octagonal table, which is surrounded by eight triangular star facets. Eight table bezels are disposed in-between the star facets and eight mid-bezels are disposed in-between the table bezels. Furthermore, the gemstone's pavilion has eight concentrically arranged culet pavilion facets, a girdle pavilion facet and a bottom small break facet that are disposed in-between the culet pavilion facets. The gemstone's girdle has eight left top half facets and eight right top half facets (located in-between the girdle bezels of the crown), and eight left bottom half facets and eight right bottom half facets (disposed in-between the girdle pavilion facets and bottom small break facets).
U.S. Pat. No. D506,946 to Ishii is titled Brilliant Gemstone, and shows an ornamental design of the gemstone.
A need exists for a gemstone cut that provides improved light returning out of the crown with limited leakage through the pavilion.
A need also exists for a gemstone cut that provides improved optical effects including brightness, scintillation and dispersion.
Thus, there exists a need for gemstone cut with improved characteristics that solves these and other problems.